In-situ silicidation metallization process

ABSTRACT

Embodiments of the invention provide a simplified method of filling contact level features formed in a semiconductor device. In general the method includes a novel method of forming a contact level feature that contains a silicide interface and a tungsten CVD deposited layer. The processes discussed below are less complex and less time consuming than other conventional contact level interconnect formation processes and thus will have an improved device yield.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent Application Ser. No. 60/663,493, filed Mar. 18, 2005 [APPM 9916L], U.S. Provisional Patent Application Ser. No. 60/683,599, filed May 23, 2005 [APPM 9916L02], U.S. Provisional Patent Application Ser. No. 60/703,538, filed Jul. 29, 2005 [APPM 9916L03], U.S. Provisional Patent Application Ser. No. 60/703,633, filed Jul. 29, 2005 [APPM 9916L04], U.S. Provisional Patent Application Ser. No. 60/709,564, filed Aug. 19, 2005 [APPM 9916L05], and U.S. Provisional Patent Application Ser. No. 60/754,230, filed Dec. 27, 2005 [APPM 9916L06], which are all herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to methods for depositing materials on substrates, and more specifically to methods for filling apertures within a high aspect ratio contact.

2. Description of the Related Art

Multilevel, 45 nm node metallization is one of the key technologies for the next generation of very large scale integration (VLSI). The multilevel interconnects that lie at the heart of this technology possess features with small CD's and high Aspect Ratios including contacts, vias, lines and other apertures. Reliable formation of these features is very important for the success of VLSI and the continued effort to increase quality and circuit density on individual substrates. Therefore, there is a great amount of ongoing effort being directed to the formation of void-free features with low contact resistance having high aspect ratios of 10:1 (height: width) or greater.

Tungsten is a metal of choice for filling contact level VLSI features, such as for example a sub-micron high aspect ratio contact (HARC) on a substrate. Contacts are formed by depositing a conductive interconnect material, such as tungsten into an aperture on the surface of insulating material disposed between two spaced-apart conductive layers. A high aspect ratio of such an opening may inhibit deposition of a conformal conductive interconnect material to fill an aperture. One simplified example of a conductive interconnect is typical MOS device shown in FIG. 1. In the illustrated MOS structure, the conductive N+source and drain regions 102 and 104 are formed in a P-type silicon substrate 100, which are adjacent to the field oxide portions 106. A gate oxide layer 108 and a polysilicon gate electrode 110 are formed over silicon substrate 100 in between source and drain regions 102 and 104 with oxide spacers 112 formed on the sidewalls of polysilicon gate electrode 110. A dielectric material 122 may be deposited over the formed structure and etched to provide a contact level aperture 120. The contact level apertures 120 are then filled with a thin barrier layer 105 and a contact material 107. The barrier layer 105 may be tungsten, cobalt or titanium and titanium nitride stack that is typically deposited using a physical vapor deposition (PVD) process. The contact material 107, which is typically a tungsten containing layer, is formed using a chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques. After depositing the barrier layer 105 a silicide layer 103 is formed at the interface of the source and drain regions 102 and 104 by allowing the deposited barrier layer 105 metal to form a silicide during a high temperature thermal anneal step (e.g., ˜800-1000° C.). The contact level apertures 120 thus provide a low resistance interconnect between various parts of the device (e.g., source region, drain region) and the layers above (not shown).

Contact level metallization processes require the formation of a silicide at the doped silicon source or drain interface to reduce the contact resistance and thus improve the speed of the formed device(s). Typically, conventional contact level metallization process(es) require the time consuming and complex process steps of depositing a metal layer that will form a silicide at the doped silicon interface (e.g., source or drain interface), removing the excess metal layer from the “Yield” (e.g., top surface of the substrate in which the features are formed) by use of a chemical mechanical polishing (CMP) type process, performing a high temperature anneal process to form a metal silicide layer, depositing a liner/barrier layer (e.g., titanium nitride (TiN), titanium (Ti), tantalum (Ta), tantalum nitride (TaN)) over the formed metal/metal silicide layer, and then filling the contact feature formed in the dielectric layer with tungsten (W) using a tungsten hexafluoride (WF₆) chemical vapor deposition (CVD) process. Since the contact level metallization process is relatively complex and requires a number of process steps, the chance of misprocessing the substrate or the chance that contamination will affect the device yield is very high.

A need exists for a less time consuming and less complex method of forming a contact level interconnect that has a silicide formed at the doped silicon interface. There is also a need for a process of forming a contact level interconnect that is less likely to be misprocessed and has improved device yield due to reduced chance of contamination during processing.

SUMMARY OF THE INVENTION

The present invention generally provide a method for depositing a material on a substrate, comprising providing a substrate that has one or more contact level features that have an exposed doped silicon containing region, selectively depositing a metal containing layer over a surface of the exposed doped silicon containing regions, and depositing a tungsten layer on the metal layer at a temperature between about 300 ° C. and about 450° C., wherein during the process of depositing tungsten layer a metal silicide is formed at the surface of the exposed doped silicon containing region.

Embodiments of the invention further provide a method for depositing a material on a substrate, comprising positioning a silicon containing substrate that has one or more contact level features that have an exposed doped silicon containing region, pretreating the exposed doped silicon containing region, wherein the pretreating process is adapted to remove an oxide layer from the exposed doped silicon containing region, depositing a metal containing layer over a surface of the exposed doped silicon containing regions, and depositing a tungsten layer over the metal containing layer at a temperature between about 300° C. and about 450° C., wherein during the tungsten layer deposition process a metal suicide is formed.

Embodiments of the invention further provide a method for depositing a material on a substrate, comprising positioning a silicon containing substrate that has one or more contact level features that have an exposed doped silicon containing region, pretreating the exposed doped silicon containing region, wherein the pretreating process is adapted to remove an oxide layer from the exposed doped silicon containing region, depositing a nickel containing layer over the bottom surface of the one or more contact level features, forming a nickel silicide layer by exposing the deposited nickel containing layer and silicon containing substrate to temperatures greater the 250° C., depositing a cobalt containing layer over the nickel silicide layer, and depositing a tungsten layer on the cobalt containing layer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 illustrate schematic cross-sectional view of a MOS type integrated circuit formed by a process described in the art;

FIG. 2 illustrates a flow chart depicting an electroless deposition process as described within an embodiment herein;

FIG. 3A-G illustrate schematic cross-sectional views of an integrated circuit formed by a process to cap a defect within a contact plug described within an embodiment herein;

FIG. 4 illustrates a flow chart depicting an electroless deposition process as described within an embodiment herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the invention provide a simplified method of filling contact level features formed in a semiconductor device. In general the method includes a novel method of forming a contact level feature that contains a silicide interface and a tungsten CVD deposited layer. The processes discussed below are less complex and less time consuming than other conventional contact level interconnect formation processes and thus will have an improved device yield.

1. Silicidation During Tungsten Deposition Process

FIG. 2 illustrates a series of method steps 1000 that may be used to fill a contact level feature. FIG. 3A illustrates a cross-sectional view of substrate 1500 having a contact level aperture 1510 formed into dielectric layer 1504. The dielectric layer 1504 contains an insulating material that includes silicon dioxide, silicon nitride, SOI, BPSG, silicon oxynitride and/or carbon-doped silicon oxides, such as SiOxCy, for example, BLACK DIAMOND™ low-k dielectric, available from Applied Materials, Inc., located in Santa Clara, Calif. Contact level aperture 1510 may be formed in dielectric layer 1504 using conventional lithography and etching techniques to expose the silicon junction 1502, such as a MOS type source or drain interface. Silicon junction 1502 is generally a doped silicon region, such as a N+or P+doped silicon region.

An oxide surface 1512 is usually formed at the silicon junction 1502 during previous etching and ashing processes used to form contact level aperture 1510. Oxide surface 1512 may be a continuous layer or a discontinuous layer across the surface of silicon junction 1502 and include a surface terminated with oxygen, hydrogen, hydroxides, a metal or combinations thereof. In examples wherein silicon junction 1502 contains a silicon-containing material, oxide surface 1512 is usually a silicon oxide surface. Also, in examples wherein silicon junction 1502 contains a metal-containing material, oxide surface 1512 is usually a metal oxide surface.

The first step of the method steps 1000 includes a pretreatment process step 1002, to remove the oxide layer so subsequent processes can be preformed on the surface of the silicon junction 1502. In this process step the substrate 1500 is exposed to a pretreatment process to form a treated surface (not shown) on the silicon junction 1502, which is substantially free of oxide surface 1512. In one example, the silicon junction 1502 contains a silicon-containing material and treated surface contains a hydride-terminus surface, such as a silicon hydride layer. In another example, the silicon junction 1502 contains a metal-containing material and the treated surface contains a reduced metal surface. The various processes that may be used to perform the pretreatment process step 1002 on the surface of the silicon junction 1502 are described below (see Pretreatment Process).

The second step of the method steps 1000 includes a metal deposition step 1004, that is used to form a metal layer 1514 over the silicon junction 1502. In one aspect, the metal layer 1514 is a nickel containing layer. The metal deposition step 1004 may be performed by use of a PVD, CVD, plasma enhanced CVD, ALD, plasma enhanced ALD or electroless deposition process to form the nickel layer. In one aspect, when a non-selective deposition process is used, such as a PVD, non-selective CVD, non-selective plasma enhanced CVD, non-selective ALD, and/or non-selective plasma enhanced ALD process(es), the method steps 1000 may include an optional nickel removal step 1006. The optional metal removal step includes the step of removing any deposited nickel from the field region 1505 (FIGS. 3A-B) by use of a wet clean process, CMP process, electrochemical process or other comparable material removal processes.

In one aspect of method steps 1000, as shown in FIG. 3C, the metal deposition step 1004 is performed using a selective nickel deposition process to deposit the metal layer 1514 over the silicon junction 1502. In this case the selectively deposited electroless nickel layer is only formed over the silicon junction 1502. An exemplary selective electroless deposition process is described below. In this case there is generally no need to perform the optional metal removal step 1006, since the metal layer 1514 will be selectively deposited at the surface of the silicon junction 1502.

The last step of the method steps 1000 is the deposit a tungsten containing layer to fill the contact level aperture 1510 using a CVD tungsten deposition process that is performed at a temperature that will cause at least some portion of the metal layer 1514 to form a metal silicide layer 1515 (e.g., NiSi, Ni₂Si). The tungsten CVD deposition process used in step 1010 is performed using conventional tungsten hexafluoride (WF₆) precursor chemistries at a temperature in the range between about 300° C. and about 450° C. Preferably, the CVD tungsten deposition process temperature range is between about 300° ° C. and about 400 ° C. Preferably, the CVD tungsten deposition process temperature is about 350° C. A conventional CVD process generally involves the simultaneous introduction of gas phase reactants, such as tungsten precursor (typically tungsten hexafluoride) and a hydrogen containing gas (e.g., H₂), near a heated wafer surface while a vacuum is applied to the system. The reaction is driven by the energy provided by the heated wafer and the free energy change of the chemical reaction. In this step a tungsten layer 1520 is directly deposited on the metal layer 1514 formed on the silicon junction 1502 during step 1004. In one aspect, the metal layer 1514 is deposited to a thickness between about 10 Å and about 100 Å. In one aspect of step 1010, at the end of the tungsten deposition process a metal silicide layer 1515 (e.g., nickel silicide (Ni_(x)Si_(y))) is formed having sufficient thickness to form a good electrical contact (e.g., ohmic contact) between the tungsten layer 1520 and the silicon junction 1502. A metal silicide layer is formed as the metal layer 1514 reacts with the silicon atoms found at the silicon junction 1502 interface, thus consuming at least a portion of the metal layer 1514 and some of the silicon atoms at the silicon junction. Since tungsten hexafluoride tends to attack the exposed metal layer 1514 during the early stages of the deposition process, it is desirable to assure that the metal layer 1514 thickness is large enough to assure that enough material remains at the silicon junction 1502 after the deposited tungsten layer 1520 has covered the exposed metal layer 1514 to assure that a good silicide contact can be formed.

2. Cobalt Containing Barrier Layer Fill Process

The second novel method, illustrated in FIG. 4, is a series of method steps 1001 that are used to fill a contact level feature. FIG. 3A illustrates a cross-sectional view of substrate 1500 having a contact level aperture 1510 formed into dielectric layer 1504. The dielectric layer 1504 contains an insulating material that includes silicon dioxide, silicon nitride, SOI, BPSG, silicon oxynitride and/or carbon-doped silicon oxides, such as SiO_(x)C_(y), for example, BLACK DIAMOND™ low-k dielectric, available from Applied Materials, Inc., located in Santa Clara, Calif. Contact level aperture 1510 may be formed in dielectric layer 1504 using conventional lithography and etching techniques to expose the silicon junction 1502, such as a source or drain interface. Silicon junction 1502 is generally doped silicon region, such as a N+ or P+ doped silicon region.

An oxide surface 1512 is usually formed at the silicon junction 1502 during previous etching and ashing processes used to form contact level aperture 1510. Oxide surface 1512 may be a continuous layer or a discontinuous layer across the surface of silicon junction 1502 and include a surface terminated with oxygen, hydrogen, hydroxides, a metal or combinations thereof. In examples wherein silicon junction 1502 contains a silicon-containing material, oxide surface 1512 is usually a silicon oxide surface. Also, in examples wherein silicon junction 1502 contains a metal-containing material, oxide surface 1512 is usually a metal oxide surface.

The first step of the method steps 1001 includes a pretreatment process step 1002, to remove the oxide layer so subsequent processes can be preformed on the surface of the silicon junction 1502. In this process step the substrate 1500 is exposed to a pretreatment process to form a treated surface (not shown) on the silicon junction 1502, which is substantially free of oxide surface 1512. In one example, the silicon junction 1502 contains a silicon-containing material and treated surface contains a hydride-terminus surface, such as a silicon hydride layer. In another example, the silicon junction 1502 contains a metal-containing material and the treated surface contains a reduced metal surface. The various processes that may be used to perform the pretreatment process step 1002 on the surface of the silicon junction 1502 are described below.

The second step of the method steps 1001 includes a metal deposition step 1004 (FIG. 3C), that is used to deposit a metal layer 1514 over the silicon junction 1502. In one embodiment, the metal layer is a cobalt containing or nickel containing layer. The metal deposition step 1004 may be performed by use of a PVD, CVD, plasma enhanced CVD, ALD, plasma enhanced ALD or electroless deposition process to form a metal containing layer. In one aspect, when a non-selective deposition process is used, such as a PVD, non-selective CVD, non-selective plasma enhanced CVD, non-selective ALD, and/or non-selective plasma enhanced ALD process(es), the method steps 1001 may include an optional metal removal step 1006. The optional metal removal step includes the step of removing any deposited metal(s) from the field region 1505 (FIG. 3A-B) by use of a by use of a wet clean process, conventional CMP process, electrochemical process and/or other comparable material removal process.

In one aspect of method steps 1000, as shown in FIGS. 3C, the metal deposition step 1004 is performed using a selective deposition process to deposit the metal layer 1514 over the silicon junction 1502. In this case the selectively deposited electroless metal layer is only formed over the silicon junction 1502. An exemplary selective electrochemical deposition of a nickel containing layer is described below. In this case there is generally no need to perform the optional metal removal step 1006, since the metal layer 1514 will be selectively deposited at the surface of the silicon junction 1502.

In one aspect, the metal layer 1514 is a nickel containing layer. For example, a nickel film is formed on the Si surface using a galvanic plating bath. To perform this process the films are created from a plating bath which contains a nickel(II) salt, such as nickel sulfate, an electrolyte such as tetramethylammonium sulfate, and a wetting agent such as diethanolamine, adjusted to basic pH with tetramethylammonium hydroxide (TMAH) and maintained at temperatures above 60° C. The wetting agent may be part of the electrolyte. No reducing agent is required to be added. During the galvanic deposition of Ni on silicon (Si), the surface of the Si acts as a reducing agent. In other embodiments, a sacrificial element or structure attached to the silicon may act as a reducing agent. The addition of a wetting agent to the galvanic system eliminates the need for galvanic displacement plating schemes on Si (see attached PDFs). Therefore, a superficial oxidation of the Si surface with a hydrochloric acid/peroxide mixture (HPM), ethanol, or other pre-treatments which allow the galvanic solution to wet the oxide free Si surface (the Si-H surface is very hydrophobic) is not needed. The formation of a nickel film on Si by this method is self-limiting, which allows a mechanism of film thickness control.

The next process step in the method steps 1001, is a step that uses a conventional thermal processing techniques to cause the deposited metal layer 1514 to form a metal silicide layer 1515 at the silicon junction 1502 (see step 1007). Typically, the conventional thermal processing techniques include performing an RTP or furnace anneal step at temperatures greater than about 250° C. for a desired period of time to cause a desired thickness of the metal silicide to form at the silicon junction 1502. An RTP system that may useful for completing aspects of this invention described herein may be purchased from Applied Materials Inc. of Santa Clara, Calif.

The next process step in the method steps 1001 is a selective barrier layer deposition step 1008 (FIG. 3F), which generally causes a metal containing layer 1518 to be deposited over the metal silicide layer 1515 formed on the silicon junction 1502. The barrier layer provides for protection of the silicide layer during the tungsten deposition process. In one aspect, the barrier layer is selectively deposited using an electroless deposition process. The barrier layer could also be a PVD tungsten layer followed by a CVD tungsten. The barrier layer deposition step 1008 may be performed by use of a PVD, CVD, plasma enhanced CVD, ALD, plasma enhanced ALD or electroless deposition process to form a cobalt containing layer in the contact level aperture 1510. In one aspect, the metal containing layer 1518 is a cobalt containing layer. In one aspect, as shown in FIG. 3F, cobalt containing layer deposition step 1008 is adapted to selectively deposit the metal containing layer 1518 on the metal silicide layer 1515. In one aspect, the selective barrier layer deposition step 1008 is performed using an electroless deposition process to selectively deposit a layer that contains, for example, a cobalt-tungsten alloy (e.g., CoW, COWP, CoWB, COWPB). An example of an electroless solution used to deposit a cobalt-tungsten alloy may contain a cobalt source, a tungsten source, a citrate source, a hypophosphite source, a borane reductant and other additives. Other electroless deposition solutions that may be used to deposit a cobalt-tungsten alloy are further described in the commonly assigned U.S. patent application Ser. No. 10/967,919, entitled, “Selective Self-initiating Electroless Capping of Copper with Cobalt-containing Alloys,” filed on Oct. 18, 2004, which is incorporated by reference to the extent not inconsistent with the claimed aspects and description herein. Exemplary electroless deposition process cell may be the same process cells/chambers as described in the capping processes described herein.

The final step in the method steps 1001 is a CVD tungsten deposition process that is used to fill the contact level aperture 1510. The tungsten CVD deposition process used in step 1010 is generally performed using conventional tungsten hexafluoride (WF₆) precursor chemistries to fill the contact level aperture 1510. In this step a tungsten layer 1520 is directly deposited on the metal containing layer 1518. A selective tungsten CVD process can also be used.

Exemplary Pretreatment Process

FIG. 3A illustrates a cross-sectional view of substrate 1500 having a via or aperture 1510 formed into dielectric layer 1504. Aperture 1510 may be formed in dielectric layer 1504 using conventional lithography and etching techniques to expose the silicon containing layer 1502, such as a source region, drain region or gate region of a MOS device. The silicon containing layer 1502 may be a silicon-containing material or a metal-containing material.

In some examples, silicon containing layer 1502 is a silicon-containing material that may also contain germanium, carbon, boron, phosphorous, arsenic or combinations thereof. For example, silicon containing layer 1502 may contain silicon, silicon carbide, silicon germanium, silicon germanium carbide, combinations thereof or doped variants thereof. In another embodiment, silicon containing layer 1502 contains a metal silicide or silicon dopant material (e.g., N-type or P-type dopants).

Substrate 1500 is exposed to a pretreatment process to form treated surface 1514 of silicon containing layer 1502, substantially free of oxide surface 1512 (not shown). In one example, silicon containing layer 1502 contains a silicon-containing material and treated surface 1514 contains a hydride-terminus surface, such as a silicon hydride layer.

In one embodiment, substrate 1500 is exposed to a wet clean process to remove oxide surface 1512 and to form treated surface 1514. In one example, oxide surface 1512 is removed by a HF-last solution to form treated surface 1514 as a substantially oxide-free, silicon hydride surface. In another example, oxide surface 1512 is removed during a liquid reduction process to form treated surface 1514 as a substantially oxide-free, metallic surface. In another example, oxide surface 1512 is exposed to a hydrogen plasma to form treated surface 1514 as a substantially oxide-free, silicon hydride surface.

During one embodiment of a pretreatment process, substrate 1500 is exposed to a wet-clean process for a predetermined time to remove oxide surface 1512 and form treated surface 1514. A wet clean process may include dispensing a wet clean solution across or sprayed on the surface of substrate 1500. The wet clean process may be an in situ process performed in the same processing cell as a subsequent electroless deposition process. Alternatively, substrate 1500 may be wet cleaned in a separate processing cell from the subsequent electroless deposition processing cell. An example of an exemplary electroless deposition processing cell is further described in the U.S. patent application Ser. No. 10/996,342 [APPM 9032], filed 11/22/2004, and U.S. patent application Ser. No. 11/043,442 [APPM 8024.P1], filed 1/26/2005, which are all incorporated by reference herein in their entirety. In one example, the wet-clean process utilizes an HF-last solution containing water, HF and optional additives including chelators, surfactants, reductants, other acids or combinations thereof. The hydrogen fluoride concentration of a wet-clean solution may be within a range from about 10 ppm to about 5 wt %, preferably from about 50 ppm to about 2 wt %, and more preferably, from about 100 to about 1 wt %, for example, about 0.5 wt %.

A wet-clean pretreatment process may occur for about 10 minutes or less, such as within a range from about 15 seconds to about 5 minutes, preferably from about 30 seconds to about 4 minutes, and more preferably from about 1 minute to about 3 minutes. During the pretreatment process, the substrate is maintained at a temperature within a range from about 15° C. to about 50° C., preferably about room temperature (e.g., 20° C.). The wet-clean process may be performed in a TEMPEST™ wet-clean system, available from Applied Materials, Inc., located in Santa Clara, Calif.

In another embodiment of a pretreatment process, substrate 1500 is exposed to a liquid reduction process containing a metal-reductant to form treated surface 1514. The metal-reductant may be a Ti³⁺ compound, such as titanium citrate. In an alternative embodiment of a pretreatment process, substrate 1500 is exposed to a plasma process for a predetermined time to reduce oxide surface 1512 and form treated surface 1514.

Exemplary Nickel Electroless Solution and Deposition Process

Nickel-containing materials are deposited on the silicon containing layer 1502 by an electroless deposition process. The electroless deposition solution to form nickel-containing materials is an aqueous solution that generally contains a nickel source, a reductant, a complexing agent, a pH adjusting agent and optional additives and surfactants. A nickel-containing material may be deposited by an electroless process utilizing either a pre-mixed electroless deposition solution or an in-line mixing process that combines solution components to generate the electroless solution. An example of an exemplary in-line mixing process and apparatus is further described in the U.S. patent application Ser. No. 11/040,962 [APPM 8926], filed 1/22/2005, which is incorporated by reference herein in their entirety.

The nickel source within the electroless deposition solution may have a concentration in a range from about 20 mM to about 200 mM, preferably from about 40 mM to about 80 mM, and more preferably from about 50 mM to about 70 mM, such as about 60 mM. Nickel sources provide nickel ions (e.g., Ni²⁺) dissolved within the electroless solution and later reduced out as the deposited nickel-containing material. Useful nickel sources include nickel sulfate, nickel chloride, nickel acetate, nickel phosphate, derivatives thereof, hydrates thereof or combinations thereof. In a preferred embodiment, nickel sulfate hexahydrate (NiSO₄.6H₂O) is used in the electroless solution to deposit nickel-containing materials.

The reductant within the electroless deposition solution may have a concentration in a range from about 1 mM to about 100 mM, preferably from about 2 mM to about 50 mM, and more preferably from about 5 mM to about 20 mM, such as about 14 mM. Reductants provide electrons to induce chemical reduction of the nickel ions that form and deposit the nickel-containing material. Reductants may include organic reductants (e.g., formaldehyde or glyoxylic acid), hydrazine, organic hydrazines (e.g., methyl hydrazine), hypophosphite sources (e.g., hypophosphorous acid (H₃PO₂), ammonium hypophosphite ((NH₄)_(4-x)H_(x)PO₂) and salts thereof), borane sources (e.g., dimethylamine borane complex ((CH₃)₂NH.BH₃), DMAB), trimethylamine borane complex ((CH₃)₃N.BH₃), TMAB), tert-butylamine borane complex (^(t)BuNH₂.BH₃), tetrahydrofuran borane complex (THF.BH₃), pyridine borane complex (C₅H₅N.BH₃), ammonia borane complex (NH₃.BH₃), borane (BH₃), diborane (B₂H₆), derivatives thereof, complexes thereof or combinations thereof. In a preferred embodiment, DMAB is used as a reductant in the electroless solution for depositing nickel-containing materials.

Chelators or complexing agents are in the electroless solution to complex nickel ions thereby stabilizing the solubility and reduction of nickel ions. The complexing agents may have a concentration in a range from about 50 mM to about 2 M, preferably from about 100 mM to about 1 M, and more preferably from about 200 mM to about 500 mM. Complexing agents generally may have functional groups, such as carboxylic acids, dicarboxylic acids, polycarboxylic acids, amino acids, amines, diamines, polyamines, alkylamines, alkanolamines and alkoxyamines. Complexing agents may include citric acid, citrates, glycolic acid, glycine, malonic acid, maleic acid, lactic acid, ethylenediaminetetraacetic acid (EDTA), ethylenediamine (EDA), triethylene tetramine (TETA), diaminoethane, monoethanolamine, diethanolamine (DEA), triethanolamine (TEA), hydroxylamine hydrochloride, ammonia, ammonium chloride, derivatives thereof, salts thereof or combinations thereof. Usually, the electroless solution contains more than one complexing agent. Preferably, the electroless solution contains at least citric acid or citrate salts, more preferably, the electroless solution also contains DEA, glycine and/or lactic acid. In one example, the electroless solution contains about 60 mM of citric acid, 115 mM of DEA, 30 mM of glycine and 120 mM of lactic acid.

A pH adjusting agent is added to adjust the electroless solution to a pH value in a range from about 8 to about 11, preferably from about 9 to about 10, and more preferably from about 9.2 to about 9.6, such as about 9.4. The pH adjusting agent may be an acidic compound to decrease the pH value of the electroless solution and include hydrochloric acid, sulfuric acid, phosphoric acid, derivatives thereof or combinations thereof. Alternatively, the pH adjusting agent may be a basic compound to increase the pH value of the electroless solution and include metal hydroxides, tetraalkylammonium hydroxides (e.g., tetramethylammonium hydroxide ((CH₃)₄NOH, TMAH) or tetraethylammonium hydroxide ((CH₃CH₂)₄NOH, TEAH)), ammonium hydroxide, DEA, TEA, derivatives thereof or combinations thereof. The pH adjusting agent may be dissolved in water prior to adjusting the pH value of the electroless solution. In one example, a 25 wt % aqueous solution of TMAH is used as a pH adjusting agent. In another example, both TMAH and DEA are used to adjust the pH value of an electroless solution.

The optional additives may include levelers, accelerators and suppressors. Levelers within the electroless solution are used to achieve different deposition thickness as a function of leveler concentration and feature geometry while depositing nickel-containing materials. The leveler within the electroless deposition solution may have a concentration in a range from about 20 ppb to about 600 ppm, preferably from about 100 ppb to about 100 ppm. Examples of levelers that may be employed in an electroless solution include, but are not limited to alkylpolyimines and organic sulfonates, such as 1-(2-hydroxyethyl)-2-imidazolidinethione (HIT), 4-mercaptopyridine, 2-mercaptothiazoline, ethylene thiourea, thiourea or derivatives thereof. The electroless deposition solution may contain brighteners or accelerators and suppressors as alternative additives to provide further control of the deposition process. The role of accelerators is to achieve a smoothly deposited surface of the nickel-containing material. The accelerator within the electroless deposition solution has a concentration in a range from about 20 ppb to about 600 ppm, preferably from about 100 ppb to about 100 ppm. Accelerators that are useful in an electroless solution for depositing nickel-containing materials may include sulfur-based compounds such as bis(3-sulfopropyl) disulfide (SPS), 3-mercapto-1-propane sulfonic acid (MPSA), aminoethane sulfonic acids, thiourea, derivatives thereof, combinations thereof. Suppressors are used to suppress nickel deposition by initially adsorbing onto underlying catalytic surfaces and therefore blocking access to the catalyst of the reaction. Suppressors generally may include polyethylene glycol (PEG), polypropylene glycol (PPG), polyoxyethylene-polyoxypropylene copolymer (POCP), benzotriazole (BTA), dipyridyl, dimethyl dipyridyl, derivatives thereof or combinations thereof. The suppressor within the electroless deposition solution has a concentration in a range from about 20 ppb to about 600 ppm, preferably from about 100 ppb to about 100 ppm.

The electroless solution may contain boric acid as an additional additive. Boric acid is added to provide additional buffering and to stabilize the composition of the solution. Boric acid is an oxidation by-product from the chemical reactions of borane reductants (e.g., DMAB). Therefore, an electroless solution containing boric acid is more normalized at the start of the deposition process since a less steep dissipation gradient exist as additional boric acid is formed from the borane reductant. Boric acid is preferably within the electroless deposition solution at concentration in a range from about 1 mM to about 50 mM, preferably from about 2 mM to about 20 M, and more preferably from about 5 mM to about 15 mM, such as about 10 mM.

Also, an optional surfactant may be added to the electroless solution. The surfactant is a wetting agent to reduce the surface tension between the electroless solution and the substrate surface. Surfactants are generally added to the electroless solution at a concentration of about 1,000 ppm or less, preferably about 800 ppm or less, such as from about 20 ppb to about 600 ppm. The surfactant may have ionic or non-ionic characteristics. A preferred surfactant includes dodecyl sulfates, such as sodium dodecyl sulfate (SDS). Other surfactants that may be used in the electroless deposition solution include glycol ether based surfactants (e.g., polyethylene glycol). For example, a glycol ether based surfactants may contain polyoxyethylene units, such as TRITON® 100, available from Dow Chemical Company. A nonylphenol ethoxylate surfactant is useful in the electroless deposition solution, such as TERGITOL®, available from Dow Chemical Company or IGEPAL-630, available from GAF Corporation. Other useful surfactants may contain phosphate units, for example, sodium poly(oxyethylene) phenyl ether phosphate, such as RHODAFAC® RE-610, available from Rhodia, Inc. The surfactants may be single compounds or a mixture of compounds of molecules containing varying length of hydrocarbon chains.

An electroless process to deposit nickel-containing materials may utilize an in-line mixing process to form the electroless solution. The process may contain the addition of two, three, four or more componential solutions to form the electroless solution. In one example, the electroless solution is formed by combining a buffered cleaning solution, a nickel-containing solution, a reducing solution and water, where each solution is a concentrate and water is added to reach a predetermined concentration of the final solution. In another example, the electroless solution is formed by combining a buffered cleaning solution, a nickel-containing solution and a reducing solution, where each of the solutions are pre-diluted and therefore do not require additional water. In another example, the electroless solution is formed by combining a buffered nickel-containing solution, a reducing solution and water, where a buffered cleaning solution and a nickel-containing solution are combined to form the buffered nickel-containing solution. Further details of in-line mixing processes and componential solutions are further described in the commonly assigned U.S. patent application Ser. No. 10/967,919, entitled, “Selective Self-initiating Electroless Capping of Copper with Cobalt-containing Alloys,” filed on Oct. 18, 2004, and published as US 2005-0136193, which is incorporated by reference to the extent not inconsistent with the claimed aspects and description herein.

A buffered cleaning solution usually contains water, at least one complexing agent, additives and a pH adjusting agent. The complexing agent within the buffered cleaning solution is at a concentration from about 0.2 M to about 3 M, preferably from about 0.5 M to about 2 M. The additive within the buffered cleaning solution is at a concentration from about 10 mM to about 1 M, preferably from about 50 mM to about 500 mM. The pH adjusting agent is at a concentration to provide the buffered cleaning solution with a pH value in a range from about 8 to about 11, preferably from about 9 to about 10, and more preferably from about 9.2 to about 9.6, such as about 9.4. In one example, a buffered cleaning solution contains water, about 1.15 M of DEA, about 375 mM of citric acid, about 300 mM of glycine, about 100 mM of boric acid and a concentration of TMAH to adjust the pH value to about 9.4. In another example, a buffered cleaning solution contains water, about 330 mM of DEA, about 300 mM of citric acid, about 150 mM of glycine, about 50 mM of boric acid and a concentration of TMAH to adjust the pH value to about 9.4.

A nickel-containing solution usually contains water, a nickel source, at least one complexing agent and a pH adjusting agent. The nickel source within the nickel-containing solution is at a concentration from about 50 mM to about 1 M, preferably from about 100 mM to about 500 mM, such as about 300 mM. The complexing agent within the nickel-containing solution is at a concentration from about 0.2 M to about 2 M, preferably from about 0.5 M to about 1 M. The pH adjusting agent is at a concentration to provide the nickel-containing solution with a pH value in a range from about 8 to about 11, preferably from about 9 to about 10, and more preferably from about 8.0 to about 8.5, such as about 8.5. In one example, a nickel-containing solution contains water, about 100 mM of citric acid, about 300 mM of nickel sulfate, about 600 mM of 85% lactic acid and a concentration of TMAH to adjust the pH value to about 9.4.

A reducing solution usually contains water, at least one reductant, at least one complexing agent and a pH adjusting agent. The reductant within the reducing solution is at a concentration from about 10 mM to about 500 mM, preferably from about 50 mM to about 100 mM, such as about 70 mM. The complexing agent within the reducing solution is at a concentration from about 1 mM to about 50 mM, preferably from about 5 mM to about 15 mM, such as about 10 mM. The pH adjusting agent is at a concentration to provide the reducing solution with a pH value in a range from about 8 to about 11, preferably from about 9 to about 10, and more preferably from about 8.0 to about 8.5, such as about 8.5. In one example, a reducing solution contains water, about 10 mM of citric acid, about 70 mM of DMAB and a concentration of TMAH to adjust the pH value to about 9.4.

The electroless solution is preferably formed by in-line mixing process that combines various volumetric ratios of the buffered cleaning solution, the nickel-containing solution, the reducing solution and water. In one example, one volumetric equivalent of a buffered cleaning solution, two volumetric equivalents of a nickel-containing solution, two volumetric equivalents of a reducing solution and five volumetric equivalents of deionized water are in-line mixed to form an electroless solution. That is, the volumetric ratio of the buffered cleaning solution, the nickel-containing solution, the reducing solution and the deionized water is 1:2:2:5. In another example of an electroless solution, a volumetric ratio of the buffered cleaning solution, the nickel-containing solution, the reducing solution and the water is 1:1:1:3.

In one embodiment, an electroless solution contains: nickel sulfate with a concentration in a range from about 20 mM to about 200 mM, preferably from about 40 mM to about 80 mM, and more preferably from about 50 mM to about 70 mM, such as about 60 mM; DMAB with a concentration in a range from about 1 mM to about 100 mM, preferably from about 2 mM to about 50 mM, and more preferably from about 5 mM to about 20 mM, such as about 14 mM; citric acid with a concentration in a range from about 5 mM to about 500 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 40 mM to about 80 mM, such as about 60 mM; DEA with a concentration in a range from about 5 mM to about 500 mM, preferably from about 10 mM to about 200 mM, such as about 33 mM or about 115 mM; glycine with a concentration in a range from about 1 mM to about 150 mM, preferably from about 2 mM to about 80 mM, and more preferably from about 5 mM to about 50 mM, such as about 15 mM or about 30 mM; boric acid with a concentration in a range from about 1 mM to about 100 mM, preferably from about 2 mM to about 50 mM, and more preferably from about 3 mM to about 20 mM, such as about 5 mM or about 10 mM; lactic acid with a concentration in a range from about 10 mM to about 500 mM, preferably from about 50 mM to about 200 mM, and more preferably from about 100 mM to about 140 mM, such as about 120 mM; TMAH with a concentration to adjust the electroless solution to a have pH value in a range from about 8 to about 11, preferably from about 9 to about 10, and more preferably from about 8.0 to about 8.5, such as about 8.5.

In one embodiment, citrate is a preferred complexing agent and is present in each componential solution, such as the buffered cleaning solution, the nickel-containing solution and the reducing solution. Citrate may be added as citric acid and/or as a citrate salt. Citrate plays an important role of buffering each of the individual componential solutions while being combined to form the plating solution. Citrates generally have poor solubility in water at high concentrations, while the componential solutions may have relatively concentrated solutions. If a substantial citrate concentration of the final electroless solution is desired, a single componential solution may not be capable of completely containing all the dissolved citrate. Therefore, the citrate may be dissolved in each componential solution to assure no formation of citrate precipitate, and subsequently combined with water forming the electroless solution at a final concentration.

The electroless deposition process may be conducted at a temperature in a range from about 35° C. to about 120° C., preferably from about 60° C. to about 100° C., and more preferably from about 80° C. to about 85° C. The water may be degassed, preheated and/or deionized water. Degassing the water reduces the oxygen concentration of the subsequently formed electroless solution. An electroless solution with a low oxygen concentration (e.g., less than about 100 ppm) may be used during the deposition process. Preheated water allows forming the electroless solution at a predetermined temperature just below the temperature used to initiate the deposition process, thereby shortening the process time.

A chamber useful to conduct an electroless deposition process for depositing a cobalt-tungsten material, a cobalt-nickel material or a nickel-containing material is the electroless deposition process cell, further described in the commonly assigned U.S. patent application Ser. No. 10/965,220, entitled “Apparatus for Electroless Deposition,” filed on Oct. 14, 2004, and published as US 2005-0081785, U.S. patent application Ser. No. 10/996,342, entitled, “Apparatus for Electroless Deposition of Metals on Semiconductor Wafers,” filed on Nov. 22, 2004, U.S. patent application Ser. No. 11/043,442, entitled, “Apparatus for Electroless Deposition of Metals onto Semiconductor Substrates,” filed on Jan. 26, 2005, and U.S. patent application Ser. No. 11/040,962, entitled “Method and Apparatus for Selectively Changing Thin Film Composition During Electroless Deposition in a Single Chamber,” filed on Jan. 22, 2005, which are each incorporated by reference to the extent not inconsistent with the claimed aspects and description herein.

Examples of Cobalt and Nickel Electroless Deposition Chemistries

Cobalt

In one embodiment, an electroless solution for depositing metallic cobalt contains: cobalt ions (CO²⁺) with a concentration in a range from about 1 mM to about 100 mM, preferably from about 5 mM to about 50 mM, and more preferably from about 10 mM to about 20 mM, such as about 15 mM; hydrazine hydrate with a concentration in a range from about 100 mM to about 2 M, preferably from about 200 mM to about 1 M, and more preferably from about 300 mM to about 700 mM, such as about 500 mM; citric acid or citrate salt with a citrate concentration in a range from about 5 mM to about 200 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 30 mM to about 70 mM, such as about 50 mM; and an optional pH adjusting agent (e.g., TMAH) with a concentration to adjust the electroless solution to a have pH value in a range from about 10 to about 14, preferably from about 11.5 to about 13, and more preferably from about 12.2 to about 12.8, such as about 12.5. In one example, a pH value is about 11.5 or higher, preferably, about 12.0 or higher, and more preferably, about 12.5 or higher. The electroless deposition process to deposit metallic cobalt may be conducted at a temperature within a range from about 35° C. to about 100° C., preferably from about 60° C. to about 90° C., and more preferably from about 70° C. to about 80° C., such as about 75° C.

Cobalt Boride

In one embodiment, an electroless solution for depositing cobalt boride contains: cobalt ions (CO²⁺) with a concentration in a range from about 1 mM to about 100 mM, preferably from about 5 mM to about 50 mM, and more preferably from about 10 mM to about 20 mM, such as about 15 mM; DMAB with a concentration in a range from about 1 mM to about 200 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 30 mM to about 50 mM, such as about 40 mM; citric acid or citrate salt with a citrate concentration in a range from about 5 mM to about 500 mM, preferably from about 30 mM to about 300 mM, and more preferably from about 50 mM to about 150 mM, such as about 100 mM; and an optional pH adjusting agent (e.g., TMAH) with a concentration to adjust the electroless solution to a have pH value in a range from about 8 to about 11, preferably from about 8 to about 10, and more preferably from about 8.5 to about 9.5, such as about 8.9. The electroless deposition process to deposit cobalt boride may be conducted at a temperature within a range from about 35° C. to about 100° C., preferably from about 60° C. to about 80° C., and more preferably from about 65° C. to about 75° C., such as about 70° C.

Cobalt Tungsten Boride

In one embodiment, an electroless solution for depositing cobalt tungsten boride contains: cobalt ions (CO²⁺) with a concentration in a range from about 1 mM to about 100 mM, preferably from about 5 mM to about 50 mM, and more preferably from about 10 mM to about 20 mM, such as about 15 mM; tungstic acid or tungstate salt with a tungstate concentration in a range from about 0.1 mM to about 10 mM, preferably from about 0.5 mM to about 5 mM, and more preferably from about 1 mM to about 3 mM, such as about 2 mM; DMAB with a concentration in a range from about 1 mM to about 200 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 30 mM to about 50 mM, such as about 40 mM; citric acid or citrate salt with a citrate concentration in a range from about 5 mM to about 500 mM, preferably from about 30 mM to about 300 mM, and more preferably from about 50 mM to about 150 mM, such as about 100 mM; and an optional pH adjusting agent (e.g., TMAH) with a concentration to adjust the electroless solution to a have pH value in a range from about 8 to about 11, preferably from about 8 to about 10, and more preferably from about 8.5 to about 9.5, such as about 8.9. The electroless deposition process to deposit cobalt tungsten boride may be conducted at a temperature within a range from about 35° C. to about 100° C., preferably from about 60° C. to about 80° C., and more preferably from about 65° C. to about 75° C., such as about 70° C.

Nickel Boride

In one embodiment, an electroless solution for depositing nickel boride contains: nickel ions (Ni²⁺) with a concentration in a range from about 1 mM to about 100 mM, preferably from about 5 mM to about 50 mM, and more preferably from about 10 mM to about 20 mM, such as about 15 mM; DMAB with a concentration in a range from about 1 mM to about 200 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 30 mM to about 50 mM, such as about 40 mM; citric acid or citrate salt with a citrate concentration in a range from about 5 mM to about 300 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 40 mM to about 60 mM, such as about 50 mM; lactic acid or lactate salt with a lactate concentration in a range from about 5 mM to about 300 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 40 mM to about 60 mM, such as about 50 mM; and an optional pH adjusting agent (e.g., TMAH) with a concentration to adjust the electroless solution to a have pH value in a range from about 8 to about 11, preferably from about 8 to about 10, and more preferably from about 8.0 to about 8.5, such as about 8.5. The electroless deposition process to deposit nickel boride may be conducted at a temperature within a range from about 35° C. to about 100° C., preferably from about 60° C. to about 80° C., and more preferably from about 65° C. to about 75° C., such as about 70° C.

Nickel Tungsten Boride

In one embodiment, an electroless solution for depositing nickel tungsten boride contains: nickel ions (Ni²⁺) with a concentration in a range from about 1 mM to about 100 mM, preferably from about 5 mM to about 50 mM, and more preferably from about 10 mM to about 20 mM, such as about 15 mM; tungstic acid or tungstate salt with a tungstate concentration in a range from about 0.1 mM to about 10 mM, preferably from about 0.5 mM to about 5 mM, and more preferably from about 1 mM to about 3 mM, such as about 2 mM; DMAB with a concentration in a range from about 1 mM to about 200 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 30 mM to about 50 mM, such as about 40 mM; citric acid or citrate salt with a citrate concentration in a range from about 5 mM to about 300 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 40 mM to about 60 mM, such as about 50 mM; lactic acid or lactate salt with a lactate concentration in a range from about 5 mM to about 300 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 40 mM to about 60 mM, such as about 50 mM; and an optional pH adjusting agent (e.g., TMAH) with a concentration to adjust the electroless solution to a have pH value in a range from about 8 to about 11, preferably from about 8 to about 10, and more preferably from about 8.5 to about 9.5, such as about 8.9. The electroless deposition process to deposit nickel tungsten boride may be conducted at a temperature within a range from about 35° C. to about 100° C., preferably from about 60° C. to about 80° C., and more preferably from about 65° C. to about 75° C., such as about 70° C.

Cobalt Nickel Boride

In one embodiment, an electroless solution for depositing cobalt nickel boride contains: cobalt ions (CO²⁺) with a concentration in a range from about 1 mM to about 100 mM, preferably from about 5 mM to about 50 mM, and more preferably from about 10 mM to about 20 mM, such as about 15 mM; nickel ions (Ni²⁺) with a concentration in a range from about 1 mM to about 100 mM, preferably from about 5 mM to about 50 mM, and more preferably from about 10 mM to about 20 mM, such as about 15 mM; DMAB with a concentration in a range from about 1 mM to about 200 mM, preferably from about 10 mM to about 100 mM, and more preferably from about 30 mM to about 50 mM, such as about 40 mM; citric acid or citrate salt with a citrate concentration in a range from about 5 mM to about 500 mM, preferably from about 30 mM to about 300 mM, and more preferably from about 50 mM to about 150 mM, such as about 100 mM; and an optional pH adjusting agent (e.g., TMAH) with a concentration to adjust the electroless solution to a have pH value in a range from about 8 to about 11, preferably from about 8 to about 10, and more preferably from about 8.5 to about 9.5, such as about 8.9. The electroless deposition process to deposit cobalt nickel boride may be conducted at a temperature within a range from about 35° C. to about 100° C., preferably from about 60° C. to about 80° C., and more preferably from about 65° C. to about 75° C., such as about 70° C.

Cobalt Nickel

In one embodiment, an electroless solution for depositing cobalt nickel contains: cobalt ions (CO²⁺) with a concentration in a range from about 1 mM to about 100 mM, preferably from about 5 mM to about 50 mM, and more preferably from about 10 mM to about 20 mM, such as about 15 mM; nickel ions (Ni²⁺) with a concentration in a range from about 1 mM to about 100 mM, preferably from about 5 mM to about 50 mM, and more preferably from about 10 mM to about 20 mM, such as about 15 mM; hydrazine hydrate with a concentration in a range from about 100 mM to about 2 M, preferably from about 200 mM to about 1 M, and more preferably from about 300 mM to about 700 mM, such as about 500 mM; citric acid or citrate salt with a citrate concentration in a range from about 5 mM to about 500 mM, preferably from about 30 mM to about 300 mM, and more preferably from about 50 mM to about 150 mM, such as about 100 mM; and an optional pH adjusting agent (e.g., TMAH) with a concentration to adjust the electroless solution to a have pH value in a range from about 10 to about 14, preferably from about 11.5 to about 13, and more preferably from about 12.2 to about 12.8, such as about 12.5. The electroless deposition process to deposit cobalt nickel may be conducted at a temperature within a range from about 35° C. to about 100° C., preferably from about 60° C. to about 90° C., and more preferably from about 70° C. to about 80° C., such as about 75° C.

While foregoing is directed to the preferred embodiment of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

1. A method for depositing a material on a substrate, comprising: providing a substrate that has one or more contact level features that have an exposed doped silicon containing region; selectively depositing a metal containing layer over a surface of the exposed doped silicon containing regions; and depositing a tungsten layer on the metal layer at a temperature between about 300° C. and about 450° C., wherein during the process of depositing tungsten layer a metal silicide is formed at the surface of the exposed doped silicon containing region.
 2. The method of claim 1, wherein the metal containing layer contains an element selected from a group consisting of cobalt and nickel.
 3. The method of claim 1, wherein the tungsten layer is deposited using a tungsten hexafluoride (WF₆) containing gas.
 4. The method of claim 1, wherein the process of selectively depositing a metal containing layer comprises electrolessly depositing a nickel-containing layer having a thickness between about 10 angstroms and about 100 angstroms.
 5. A method for depositing a material on a substrate, comprising: providing a silicon containing substrate that has one or more contact level features that have an exposed doped silicon containing region; pretreating the exposed doped silicon containing region, wherein the pretreating process is adapted to remove an oxide layer from the exposed doped silicon containing region; depositing a metal containing layer over a surface of the exposed doped silicon containing regions; and depositing a tungsten layer over the metal containing layer at a temperature between about 300° C. and about 450° C., wherein during the tungsten layer deposition process a metal silicide is formed.
 6. The method of claim 5, wherein the metal containing layer contains an element selected from a group consisting of cobalt and nickel.
 7. The method of claim 5, wherein the tungsten layer is deposited using a tungsten hexafluoride (WF₆) containing gas.
 8. The method of claim 5, further comprises depositing a cobalt containing layer on the nickel containing layer prior to depositing the tungsten layer.
 9. The method of claim 5, wherein the process of depositing a metal containing layer comprises electrolessly depositing a nickel-containing layer having a thickness between about 10 angstroms and about 100 angstroms.
 10. A method for depositing a material on a substrate, comprising: providing a silicon containing substrate that has one or more contact level features that have an exposed doped silicon containing region; pretreating the exposed doped silicon containing region, wherein the pretreating process is adapted to remove an oxide layer from the exposed doped silicon containing region; depositing a nickel containing layer over the bottom surface of the one or more contact level features; forming a nickel silicide layer by exposing the deposited nickel containing layer and silicon containing substrate to temperatures greater the 250° C.; depositing a cobalt containing layer over the nickel silicide layer; and depositing a tungsten layer on the cobalt containing layer.
 11. The method of claim 10, wherein the tungsten layer is deposited using a tungsten hexafluoride (WF₆) containing gas.
 12. The method of claim 10, wherein the cobalt containing layer is a cobalt-tungsten alloy.
 13. The method of claim 10, wherein the process of depositing a nickel containing layer comprises electrolessly depositing a nickel-containing layer having a thickness between about 10 angstroms and about 100 angstroms. 